Cold extrusion bushing

Hole extrusion strengthening is a local strengthening treatment performed on the hole wall of a hole structure at room temperature, directly or indirectly by means of extrusion strengthening tools. It causes elastoplastic deformation of the hole wall material, forming a residual compressive stress field and refining the microstructure of the hole wall. The beneficial residual compressive stress field formed on the hole wall can offset part of the tensile stress generated when the hole structure is subjected to external alternating loads, reduce the stress peak and mean stress on the hole wall of the loaded hole structure, delay fatigue crack initiation, and increase the threshold value for crack initiation on the hole wall, thereby improving the crack initiation life of the hole wall. This process features the advantages of not changing the material, shape or quality of the hole structure, as well as simple structure and convenient operation, and is widely used in the aviation and aerospace fields. Owing to its remarkable strengthening effect, hole extrusion strengthening has been extensively applied in the extrusion strengthening of key load-bearing hole structures in aircraft.